In recent years, computers are indispensable to our daily lives, business of enterprises or the like. Disaster recovery (DR) techniques are important when computer systems are damaged by unexpected disasters.
With a typical disaster recovery technique, business data are sent at a certain check point from a primary site to a secondary site, which is positioned apart from the primary site. Thereafter, when various file operations are applied to the business data at the check point in the primary site, a log recording the file operations is transferred to the secondary site. When a disaster strikes the primary site, the business data having the file operations applied are written in the transferred log in the secondary site. Therefore, it is possible in the secondary site to recover the business data to have a relatively new arbitrary state. One of the disaster recovery techniques is, for example, realized by the product name “Double-Take” (“Double-Take” is a registered trademark), manufactured and distributed by Double-Take Software Incorporation.